An optical-electronic system for automatic label identification is described in U.S. Pat. Nos. 3,225,177 and 3,612,644.
A label scanned by such a system comprises, as described in U.S. Pat. No. 3,571,571, an array of colored stripes arranged in a two-position base-four format for coding information pertaining to a vehicle to which the label is attached.
In order to eliminate unwanted reflections generated by protection material of the reflective label, the incident beam on the label should form an angle of 12.degree.-15.degree. with a normal plane to the reflective surface, as described in U.S. Pat. No. 3,456,997.
The 12.degree.-15.degree. inclination of the incident beam reduces the reflected light.
The energy loss is being justified by the elimination of unwanted reflections and by a better reading of the stripes placed in peripheral positions.